The present invention is in the field of gas analysis and more specifically relates to apparatus for measuring the concentration of gaseous nitrogen molecules (N.sub.2) in a volume by measuring the absorption of visible radiation passing through the gaseous sample.
Of all the common gases encountered in everyday life both in the medical and industrial arenas nitrogen (N.sub.2) remains one of the most difficult to detect, notwithstanding the advancement of many branches of science and technology. The Non-Dispersive InfraRed (NDIR) gas analysis technique which finds wide applications in the detection of common gases such as carbon dioxide, methane, carbon monoxide, hydrocarbons, etc., cannot be used to detect gaseous nitrogen due to the lack of suitable infrared absorption bands for this gas. Other common gas detection techniques such as fluorescence and absorptive spectrophotometry are operative for nitrogen only in the difficult vacuum ultraviolet (VUV) region because nitrogen has no spectrally specific absorption bands in the visible portion of the electromagnetic spectrum.
Despite the lack of a proficient method for the measurement of nitrogen, the gas itself is a very important one for both medical and industrial applications.